PURPOSE: To examine the methodology of worksite fitness and exercise programs and to assess their effect on health-related fitness, cardiac risk factors, life satisfaction and well-being, and illness and injury.SEARCH METHODS: The 52 studies reviewed cover English-language literature for the period from 1972 to 1994, as identified by a search of the Cumulative Index Medicus, Medline, the Canadian Sport Documentation Centre's "Sport Discus," computerized bibliography, and my own files. Reports were divided into five controlled experimental studies, 14 quasi-experimental studies with matched controls (one reported in abstract), and 33 other interventions of varied quality.SUMMARY: Methodologic problems include difficulty in allowing for Hawthorne effects, substantial sample attrition, and poor definition of the intervention (exercise or broad-based health promotion). Findings are analyzed by specific fitness and health outcomes. Program participants show small but favorable changes in body mass, skinfolds, aerobic power, muscle strength and flexibility, overall risk-taking behavior, systemic blood pressure, serum cholesterol, and cigarette smoking. Claims of improved mood state are based heavily on uncontrolled studies. Quasi-experimental studies suggest reduced rates of illness and injury among participants, but seasonal and year-to-year differences in health weaken possible conclusions.CONCLUSIONS: Participation in worksite fitness programs can enhance health-related fitness and reduce risk-taking behavior, but population effect is limited by low participation rates.